Pretty simple question I think: When dpsing an aoe pack and looking for cleave damage from Ignite, should I just focus one target that will last the longest? I find myself at times tab-targeting to keep my aggro down, but I got to thinking that this might be the worst thing I could do. Any insight into this would be appreciated.

Notes
Ignite deals damage every second, and refreshes to a maximum duration of 10 seconds.
Ignite cannot critically strike and is unaffected by Haste.
Spread Mechanics
Ignite will attempt to spread itself to any nearby enemy within approximately 8 yards, regardless of whether or not the enemy is in combat. This includes Neutral mobs.
If an Ignite is attempting to spread itself to a target that is already affected by an Ignite of lesser damage by the same Mage, it will overwrite that Ignite.
If an Ignite is attempting to spread itself to a target that is already affected by an Ignite of greater damage by the same Mage, it will fail and be overwritten by the larger Ignite.
Ignite can spread to multiple targets at once, and has no limit on how many targets it can spread to so long as they are in range.
When Ignite spreads to another target, it matches its remaining duration from the target it spread from.